ATmega8 Atmel Corporation, ATmega8 Datasheet - Page 19

• Manufacturer Part Number: ATmega8
• Manufacturer: Atmel Corporation

Specifications of ATmega8

• Flash (kbytes): 8 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 23
• Ext Interrupts: 2
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 1
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 3
• Input Capture Channels: 1
• Pwm Channels: 3
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

Data Memory
Access Times
EEPROM Data
Memory
EEPROM Read/Write
Access
2486Z–AVR–02/11
This section describes the general access timing concepts for internal memory access. The
internal data SRAM access is performed in two clk
Figure 9. On-chip Data SRAM Access Cycles
The ATmega8 contains 512bytes of data EEPROM memory. It is organized as a separate data
space, in which single bytes can be read and written. The EEPROM has an endurance of at
least 100,000 write/erase cycles. The access between the EEPROM and the CPU is described
below, specifying the EEPROM Address Registers, the EEPROM Data Register, and the
EEPROM Control Register.
“Memory Programming” on page 215
in SPI- or Parallel Programming mode.
The EEPROM Access Registers are accessible in the I/O space.
The write access time for the EEPROM is given in
however, lets the user software detect when the next byte can be written. If the user code con-
tains instructions that write the EEPROM, some precautions must be taken. In heavily filtered
power supplies, V
some period of time to run at a voltage lower than specified as minimum for the clock frequency
used.
these situations.
In order to prevent unintentional EEPROM writes, a specific write procedure must be followed.
Refer to
When the EEPROM is read, the CPU is halted for four clock cycles before the next instruction is
executed. When the EEPROM is written, the CPU is halted for two clock cycles before the next
instruction is executed.
See “Preventing EEPROM Corruption” on page 23.
“The EEPROM Control Register – EECR” on page 20
Address
clk
CC
Data
Data
WR
CPU
RD
is likely to rise or fall slowly on Power-up/down. This causes the device for
Compute Address
T1
Memory Vccess Instruction
contains a detailed description on EEPROM Programming
Address Valid
CPU
T2
Table 1 on page
cycles as described in
for details on how to avoid problems in
for details on this.
Next Instruction
T3
21. A self-timing function,
ATmega8(L)
Figure
9.
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